Preparation of vinyl esters of a stabilized rosin acid



Patented Oct. 21, 1952 UNITED STATES PATENT OFFICE JPREPARATIONIOF VINYL ESTERS OF A STABILIZED ROSIN A'CID John C."Robinson,:.lr., Wilmington, Del., assignor toHerculcsP-owder Company, Wilmingtom-Dh, a corporation .of Delaware No Drawing. =Applicatiori February 18,1950,

i'SerialJNo. 145,080

I7.Y.C1.'ims. (Cl. 260-400) This inventionrelatesrto agprocess for the manufacture :of .vinyl esters of carboxylic acids. More particularly, .it relates to a, process ior' the manufacture of vinyl esterswof .rosin acids.

Various procedures :areaknown for theproduction 4 of vinylresters of carboxylic acids generally. One-f these procedures involves thenacidolysis of vinyl acetate using a .desired carboxylicacid havingat least .3 carbon atoms. inthe presence of aamercury catalyst. Another procedure, and one to which this invention ,particularly .relates,

is that which involves :therreaction of .acetylene with the desiredwaci'd in the presence -of.-a car- 'boxyliclacid salt of-;zinc ori'cadmium. Thismeth- 1 od 'is' that described inlU Patent No.-2,066,0'75.

' It is stated in said U. S. Patent i No. .2 $66,075 that 'rosin' oriabietic :acidi'may be reacted with acetylene in the presence of a 'carboxylic acid salt of "zinc or cadmium .:as catalyst andunderthe conditions there described as: generally applicable to all carboxylic'acids of 5 carbon atoms or higher to yield the vinyl ester: of rosin or::abietic: acid.

This. statement, however, is subject to-.-consider- "able qualificaticn era-limitation. While itvis true 'that' the vinyl ester 'of "rosin ;or -:abetic.-1acid-can be prepared by. thevprocedure of- U; S. Patent No. 2,066,075;the:crude ester product obtained direct- 1y from. the acetylene treatment :cannot: be. distilled either at atmospheric-or reduced pressure to isolate the desired vinyl ester of rosin or abietic acid. Any attempt to do'so results in the entire mass setting up solid inthe: distillatlonpotvwith no actual distillation takingriplace. It-isp0ssible to achieve a "distillable mass vby subjecting the crude ester product to :aseries :of' extractions .-in-

volving extractions with aqueous :mineral acid followed by extractions .with aqueous ialkali. Such operation is,however, exceedingly-cumbersome for use in'practical commercial operations. 'Fu'r'thermorause of the extraction techniquexcuts down on the yield substantiallyascwill xbeiapparent from what follows.

"I have recently io'undsthat for some unexplained reason'lt is'onlyf'necessary torgive the rosin a preliminary treatment whichtwill :have

the efi'ect of chemicallyr'stabilizing it in "order to avoid the above=mentioned-rextraction steps and make possible the direct distillation of the: crude ester product -to yield the desired-vinykesteraoi the chemically stabilizedrosin. .By a chcmical stabilization treatment, there is meant either hydrogenation of the resin to provide a hydrogenatedrosin-or dehydrogenationxof the rosin -=to provide a I dehydrogenated -rosin. '.'-Itis -:.well "-k-nown to the art that: either thes'hydrogenation or the dehydrogenation. of a rosin has .a 1 stabilizing eifect thereon in the sense that theproductsof such treatments are much ,more stable .to air oxidation than are .therosins from .-which they are derived. The :reason, however, for the .sta- .bilization treatments having .the effect which provides (the basis forithis inventionis :quite ob- .Broadly expressed, this inventioncomprisesa .process for preparing avi-nyl ester of. a rosinacid which in turn comprises-subjecting -.a rosin acid to achemical stabilization: treatmentwhich may lee-either a hydrogenation. treatment or .a. ,dehy- .drogenation treatment, contacting the resulting chemically .stabilized rosin acid in liquid phase with acetylene in the presenceof. a earboxylicfacid salt .of zinc, mercury .or. cadmium as catalyst,

and separating the resulting vinyl ester .of the chemically stabilized-rosinacid fromthe other ingredients of the reaction mixture .by ..distillation. Theother ingredients ofthe reaction-mix- .turewlllcomprise unreacted:stabilizedrosin, acid, catalyst, acetylene polymerapolyiners .of the vinyl ester of stabilized rosin acid, possiblycomplexes of the catalyst with the aforementioned ingredients, .etc. The distillation ,.is,.preferably carried out in vacuo to avoid excessive polymerization.

Anycarboxylic acidsaltof .zinc, mercury or cadmium .may. be. employed, incarrying out 1 the invention. Examples. of, such ,salts .are. zinc acetate,v zinc stearate, .zincbenzoate, cadmium benzoate, :the. zinc," mercuric and .cadmium salts of :hydrogenated. rosin. .acid, the zinc, m ercuric and cadmium salts of ,dehydrcgenated rosin acid, .mercuric acetate, .mercuricphosphate, ,etc. .lThewsalts may be added as such to the stabilized-rosin acid tov be treatedlwithracetyleneior theyimay bev .pre-

.pared. by dissolvingthe. oxides. of. zinc, mercury or. cadmium in the .particularstabilized rosin acid to the employed. Generally speakin the zinc salts arepreferred- .in view, of .the, fact, that ,the

reaction proceeds withgreater rapiditycwithnsuch catalysts. 45.

form. In. general, somewhatlower reaction tem- 7 When Qmercury -,s.alts are employed, .they :are preferably employed in the ,mercuric peratures-maybe effectivelyemployed'yvhen mercury salts are...used as; catalysts .as compared with -operations usingzincv 0r..cadmium catalysts.

Having ,described the. invention in its broadest aspects, the iollowinglexamples,aregiven as illustra'tive embodiments .-.thereo.f They .should, not

beiconsideredasilimitingwthe. invention; however,

. but merely. as, specific embodimentsoi ,jthe Lbroad ,concept. All partsand percentages in this speci- 3 flcation and claims are by weight unless otherwise indicated. The pressures mentioned in the examples (microns Hg and mm. Hg) have reference to absolute pressure.

Example 1 A dehydrogenated rosin was prepared by heating N wood rosin with a platinum catalyst in the absence of added substances capable of reducing the unsaturation thereof. The resulting product had a dehydroabietic acid content of about 45% and an abietic-type resin acid content of To 100 g. of the above dehydrogenated rosin in a fiask were added 4.5 g. of anhydrous zinc acetate. The mixture was heated to 200 C. while being sparged with nitrogen. After the acetic acid had been purged out of the mixture, about 55 cc. of the product were placed in a 110 cc. stainless steel, rocking-type autoclave. The autoclave was flushed with nitrogen. Thereafter, additional nitrogen was forced in to provide a pressure of 40 p. s. i. (gage). When the autoclave had reached a temperature of 230 C., acetylene Was admitted at tank pressure, 250-300 p. s. i. (gage). When the pressure had dropped about 100 p. s. i., it was raised back to top tank pressure and the procedure repeated as long as gas was being absorbed. When the rate of gas absorption had nearly stopped (about 4 hours after starting the introduction of acetylene) the gas was bled off once and replaced with fresh acetylene and the run continued. The overall period of elapsed time from the start of the introduction of acetylene to the final bleeding off of acetylene was about 7 hours. The autoclave was then cooled and the crude product removed. The crude product was filtered to remove a small amount of catalyst which had precipitated. This crude product was then distilled directly to provide a relatively pure vinyl ester of dehydrogenated rosin boiling at from 160 C. to 190 C. at 0.5 to 1.0 mm. Hg (absolute). This distilled product was a pale yellow-colored liquid having an acid number of 0. It was obtained in the amount of '25 g. which amounted to a yield of 70% based on the dehydrogenated rosin used as starting material.

Example 2 .A hydrogenated rosin was prepared by subjecting N wood rosin to hydrogen in the presence of a Raney nickel catalyst. The resulting product was one which was about 45% saturated with hydrogen and which had an abietic acid con- 1 of acetylene to the first point at which acetylene absorption had nearly stopped was about 4 hours. The overall period during which acetylene was introduced into the autoclave was about 6 hours. The crude product obtained was distilled to provide a relatively pure vinyl ester of hydrogenated rosin boiling at from 180 C. to 210 C. at 1 mm. Hg (absolute). The distilled product was a pale yellow-colored liquid having an acid number of 0. It was obtained in the amount of 77 g. which amounted to a yield of 71% based on the hydrogenated rosin used as starting material.

Ex mple 3 The same type of dehydrogenated rosin was used in this experiment as was used in Example 1.

The autoclave used in this experiment was different from that of the preceding two experiments. It was a much larger autoclave in which 600 g. batches could be conveniently handled. The autoclave, designed to take care of dangerous exothermic reactions, had an in-built wide rupture disc and an internal cooling coil. It was of the rocking type.

Five hundred grams of the dehydrogenated rosin, cc. of toluene, and 44 g. of anhydrous zinc acetate were charged into the autoclave and the mixture heated to 210-220 C. After heating the mixture at this temperature for 10-15 minutes, the vent line of the autoclave was opened whereupon acetic acid and a little toluene were allowed to escape. Acetylene was then introduced into the autoclave at tank pressure, 250- 300 p. s. i. (gage). Since traces of acetic acid were left in the rosin-catalyst-solvent mixture, the initial reaction appeared to result in the formation of vinyl acetate. This compound, a relatively high vapor pressure liquid, reduced the partial pressure of the acetylene in the autoclave such that despite a total pressure of 250 p. s. i. (gage) from the acetylene reservoir the reaction rate was appreciably diminished. Hence, the acetylene-vinyl acetate vapor was bled out of the autoclave after 1'0-15 minutes of operation and the autoclave repressured with acetylene. The reaction was continued until the reaction had substantially stopped as evidenced by the acetylene pressure. The total period of introduction of acetylene amounted to about 6 hours.

The crude product so obtained was distilled to give a relatively pure vinyl ester of dehydrogenated rosin boiling at C. to C. at 1 mm. Hg (absolute). In this manner 339 g. of distilled vinyl ester of dehydrogenated rosin were obtained. This corresponded to a yield of 87% based on the dehydrogenated rosin used as starting material. The distilled product was a pale yellow-colored liquid having an acid number of 0.

Example 4 The same hydrogenated rosin was employed as that used in Example 2. However, the equipment employed was that used in connection with Example 3. The starting materials and the amounts thereof were the same as in Example 3 with the exceptions (1) that the dehydrogenated rosin was replaced with hydrogenated rosin and (2) 0.5 g. of p-tertiarybutyl catechol was added as a polymerization inhibitor. The conditions of the reaction were essentially the same as those of Example 3. The crude product resulting was distilled to provide a relatively pure vinyl ester of hydrogenated rosin which boiled at from 160 C. to 190 C. at 1 mm. Hg (absolute). This distilled product was obtained in the amount of 270 g. which corresponded with a yield of 73% based on the hydrogenated rosin employed as starting material. It was a pale yellow-colored liquid having an acid number of 0.

Example 5 A hydrogenated rosin was preparing by subjecting N wood rosin to hydrogen in the presence of a palladium-on-charcoal catalyst. The resuiting-product was one-which-was 98% saturated with hydrogen and which had. an abietic-type resin acid content of The: equipment employed was that utilized in Example 3. The starting. materials and, the amounts thereof were the same as thosein Example-3 withtheexceptions (1) that the dehydrogenated rosin wasreplaced with hydrogenated rosin. (2-) that430 g. of hydrogenated rosin were hydrogenated .:rosin: acid: which: is: at:.1.east.-.140.%; saturated: with. hydrogen; and: which has a; cont nt f ab ic-tyne resinacids; of. not 1v. r:1.0.% .-v It is most preferred; to; employa hydrogenated, rosin acid havinga: contentofjabietic=type resinacids of substantially 0.

Per cent saturation with hydrogen as applied to any particular sample of hydrogenated rosin acid means 100% X'No. of. g. of. H absorbed per 100 g. of' the initial rosin acid? in. Preparing the sample Nofof g, of H ab orbedpfIO O afar. the initial rosin were preparing aconipletely saturated rosin acid;

used, and- (3) that 35 g. of'catalystwere used.

The: crude product obtained'in this: manner was.

distilled to yield arelatively pure-vinyl ester of; hydrogenated rosin boiling between 160 C. and 190"C; atl mm. Hg (absolute). The distilled product was obt'ainedin the amount of. 216 g. which corresponded with a yield of 64% based on the hydrogenated rosinused'as starting material. The distilled product was a pale yellowe colored liquid having-anacid' number of 0.

Example 6 Example -3 was-repeated using N wood rosin in commercial'rosins', which are known mountain 2.

neutral body fraction as well as a rosin acidfraetion, and=the rosin acidfractionsobtained therefrom. Thus, there is included wood rosin, gum rosin, and the substantially entirely acidic fractions obtained therefromas .by distillation, combination saponification andv extraction processes, etc: It is well known, too, thatthe acidicfraction contained in wood orgum rosin is a mixture of isomeric resin acids; which include abietic. levopimaric, dextropimaric, neoabietic, isodextropimaric, etc; acids. Such specific compounds are-equivalentto thenaturally occurringmixtures found in wood or gum rosin for presentgpurposes and the term rosin acid is intended to be inclusive; thereof; however, from an economic standpoint, the naturally occurring woodv or gum rosin or-acidic fractions thereof are preferred.

Tall oilis well known to contain resin acids, fatty acids and a variety of nonacidio constituents. The resin acid fraction derived from tall oil is the equivalent of wood or gum rosin formany purposes, and for the purpose of this invention that equivalency exists. Accordingly, for present purposesthe resin acid fraction of tall oilis tobe considered asa. rosin acid.

Thehydrogenated rosin acids employed in accordance with this invention may be made by any, ofthe known proceduresfor hydrogenating rosin. acids. A examples thereof, there may be men-, tioned the procedures of U. S. 2,094,117 and U. S. 2,155,036. Other procedures which are of interest arethosedescribed in U. S. 2,174,651; U. S. 1,973,- 865'; U; $2,113,808; and U. S. 2,346,793.

Rosin acids of various degrees of hydrogenation may be usedrin preparing vinyl esters in accordance with. this invention. In general, any ofthe prior art hydrogenated rosin acidsmay be employed; It ispreferred, however, toemploy a.

A completely-saturatedrosin acidi is one .prer paredfunder suchstrenuous COI'ldiiliOIlS'Of'hYdI'O? genation that.substantially.= all" of. the ethylenic:

double-bonds contained in thestarting rosin acid are saturated with hydrogen. The, analytical;

procedure used to efiect complete; saturation of-a: rosin acid is described in detail infra.

As stated above, itiis preferred: thatthehydro genated rosin acid employed have a. content of abietic-type resin acids of not over 10%, and

mostpreferred that the content of-abietic-type resin acids be substantially 0. By: abietic-type resin acids there is meant the classofresin acids having the carbon skeleton of'abieticacid',

CH3 00 OH;

and having two ethylenic double bonds per mol; ecule.

' acid, levopimaric acid, and'neoabietieacid, This class of resinacids is sometimes describedinthe, literature as acidsof the levopimaric acid-abietic acid structural, group.

The dehydrogenated rosin acidsused ,in accord? ance with this invention may be prepared. accord ing to known procedures. As exemplary ofjknown.

procedures of dehydrogenating rosinacids thereis mentioned the heating of rosin acid. for oneto two hours at C. to.2 00 C; with a dehydrorgenation catalyst such as iodine or. sulfur, inthe, amount of 0.5'to 4% of the rosin acid. Dehydror. genated rosin acidsmay also, be produced by. what.

is known in the art as thedisproportionationi? reaction. A disproportionated rosin. acid; isv a.

rosin acid thatv has been treated with an active.

hydrogenation catalystunder conditions of ,r eaction, adapted to produce an intra: andintermolecular rearrangement. of thehydrogen atoms,

in the rosin acids contained, therein, andin the absence of added, substances capableof reducing.

the unsaturation of the rosin acidnnderthe C0111 ditions. of treatment, rosin acids have asubstantialproportion of'dehydrogenated acidic constituents and: are prop erly-regarded as dehydrogenatedlrosin acids. See in this connection. U. S. 2;l54,629 to Littmamr.

Othermaterials which are properly classed as dehydrogenated rosinv acids and which. can be;

used as such, in, accordance with this invention are pyroabietic acid, which isrich in, dehydro-- Resin acids falling in this classare abietic.

Such disproportionated,

dehydrogenated rosin acids provide products having a rather wide variety of degrees of dehydrogenation. It will be understood in this connection that the resin acids present in wood and gum rosin are substantially entirely isomeric compounds possessing the empirical formula These isomers possess two ethylenic double bonds per molecule. Upon subjection to the known dehydrogenation processes a portion of the isomeric acids loses two atoms of hydrogen and it is believed that the resulting three ethylenic double bonds arrange themselves in the form of the most stable configuration, the benzene ring. Such acids have the empirical formula CzoHzsOz and are commonly referred to as dehydroabietic acid." The dehydroabietic acid content of a dehydrogenated rosin acid may be ascertainedby subjecting the same to ultraviolet absorption analysis. Obviously, the content of dehydroabietic acid of a dehydrogenated rosin acid is a measure of the degree of dehydrogenation of the original rosin acid.

As explained above, rosin acids having a variety of degrees of dehydrogenation result from the procedures for dehydrogenation described in the art. In general, any of the prior art dehydrogenated rosin acids may be employed in practicing this invention. It is preferred, however, to employ one having a dehydroabietic acid content of at least 40% and having an abietic-type resin acid content of not over 10%. It is still further preferred to employ a dehydrogenated rosin acid having a content of abietic-type resin acids of substantially 0.

Some reaction can be effected between a chemically stabilized rosin acid and acetylene at atmospheric pressure and pressure slightly thereabove. However, to achieve practical rates of reaction it is necessary to employ a pressure of at least 50 p. s. i. (gage). The preferred pressure to employ is one within the range of from about 100 to about 300 p. s. i. (gage). Still higher pressures may be employed if desired.

A temperature of at least 150 C. should be employed to achieve practical reaction rates. However, still lower temperatures are operable if the length of the reaction period and the extent of polymerization of the vinyl ester are of no concern. Thus, it must not be concluded that the figure 150? C. is a critical figure below which reaction is not obtained. The temperature employed should not be so high that substantial decomposition of the stabilized rosin acid takes place. It is preferred, taking into account the matters of practical reaction rate and safety, to employ a temperature within the range of from about 190 C. to about 250 C.

In connection with the use of superatmospheric pressure, it is pointed out that under certain conditions of temperature and pressure acetylene is explosive. No attempt is made herein to delineate the explosive ranges. However, when carrying out this invention under superatmospheric pressure, it is desirable, particularly dur-. ing the first part of the reaction period, to dilute the acetylene with an inert gas such as nitrogen, hydrogen, carbon monoxide, methane, ethane, etc.

' It is also desirable to operate by remote control behind a substantial barricade.

In the specific examples'hereof it is noted that undiluted acetylene was used even though the reactions were carried out at superatmospheric pressure. The fact that no detonations occurred is attributed to the use of well grounded equipment and a relatively small quantity of material. Other factors of importance were the use of small diameter pressure tubing and the absence of copper lines. It ordinarily takes a spark, copper acetylide or a sudden increase in pressure to detonate acetylene. In any event it is strongly recommended that in carrying out the examples the equipment be isolated by barricades and that it be operated by remote control.

As further illustrated by the examples, an inert solvent for the chemically stabilized rosin acid may be employed if desired. The employment of solvents is advantageous from the standpoint of ease of handling of the reaction mixture. There is also evidence of less polymerization of the vinyl esters when a solvent is employed. Any solvent for the chemically stabilized rosin acid which at the same time is inert to the acetylene under the conditions of reaction may be employed. Thus, aromatic hydrocarbons such as benzene, toluene, xylene, etc., aliphatic hydrocarbons such as hexane, heptane, isooctane, etc., and solvents such as tetrahydrofurane, dimethylformamide, etc. may be employed.

The catalyst employed, as stated previously, is a carboxylic acid'salt of zinc, mercury or cadmium. With respect to the amount of the catalyst to employ, there should in general be employed sufficient of the salt such that it does exert a definite catalytic effect on the reaction with which this invention is concerned. In other words, it can be said that a catalytic amount of the salt should be used. No particular minimum amount can be set which will be generally applicable to all carboxylic acid salts of zinc, mercury or cadmium having a catalytic effect on the subject reaction, there being some variation in the applicable minimum in going from one salt to another. However, in order to achieve practical reaction rates, experience has shown that from about 0.02 to about 0.23 mol of the zinc, mercury or cadmium salt should be employed per mol of chemically stabilized rosin acid. Of course, molar ratios greater than 0.23 can be employed if desired. There appears to be no particular advantage, however, in going to these higher ratios. The preferred range of catalyst concentration is from about 0.03 mol to about 0.14 mol of the zinc, mercury or cadmium salt per mol of chemically stabilized rosin acid.

Distillation of these esters should be carried out in a leak-proof vacuum system. Pale colored esters distill over readily above C. at 1 mm. pressure (absolute) until all of the volatiles have passed over. At this point further heating of the residue causes a sharp rise in temperature with attendant thermal decomposition and loss in vacuum.

The significant advantage of the process of this invention lies in the fact that the crude ester product resulting from the vinylation step is directly distillable. Heretofore, when rosin acid was used as. the acid to be vinylated, it has been necessary to subject the crude ester product to a series of extractions with aqueous mineral acid and aqueous alkali to provide a distillable product. The subject process entirely avoids these intermediate extraction steps and provides a crude ester product which is directly distillable. Furthermore, substantially higher yields of distilled vinyl ester of chemically stabilized rosin acid are obtained in the subject process as compared with the prior art process in which rosin acid per se is employed. Using rosin acid per se without any chemical stabilization treatment 1 acid.

prlor 't-to 'zvlnylation, ithe yields of distilled tvinyl ester of rosin :acidultimately obtained are 60 to 65% ibased on":the .rosin'acid, whereas .using chemically .istabilized rosin acids in accordance with :this invention, .the yields are normally 70% to 85% basedion the chemically :st'a'bili'zed rosin The analytical method referredto supra 'for xquantitativelycompletely hydrogenating a rosin 'acidis thefollowing. This method effects re-, imoval of :all .unsaturation of the rosin acid existabout '.1:hour.) ,the mercurysurfaces in'the buret F are leveled 1 using the mercury reservoir; This condition of complete reduction is determinedlby reading the leveled mercury volume at 30-minute intervals until the volume is constant within 'Whencomplete reduction of the .Pt has been achieved, record the gas volume, temperature,

and baromet'ricpressure. The gasvolume at this point should not bemore than 45 ml. -Rotate;the side arm so as to allow the samplecup to vdrop into'theiacetic acid solution. Permit hydrogena- "tion to proceed for about 16 hours. [Read the final gas volume, temperature,"and' pressure.

. Temperature is :readto the-nearest 10.1 Grand the' pressure to thenearest 1 mm. Correct the initial and final gaswolumes to standard conditions, :first adding the' volume of the uncalibrated system.

(Corrected initial volume correctediinal volume) 0.00900 percent H absorbed The reagents employed are (1) acetic acid, empyreuma-free (passing dichromate test), (2)

platinum oxide catalyst of the type described by 'Voorheesand Adams, J. A. C. 8., 44, 1397 (1922), and by Adams and Shriner, J. A. C. S., 4.5, 2171 (1923), and (3) commercial hydrogen.

The apparatus employed includes a gas measuring buret, a reaction flask, and a magnetic stirrer. The gas buret employed is that described by C. R. Noller and'lvl. R. Barusch, Industrial and Engineering Chemistry, Anal. Ed, vol.

14, 907 (1942), with the exceptions (1) there is a end (within the flask) is so made as to permit a A sample cup placed thereon to drop to the bottom of the flask when the stopper handle is turned 90 degrees.

Remove the side arm of the reaction flask and weigh in 0.10 i 0.01 g. PtO catalyst. Add a glassencased iron wire and wash the catalyst into the flask with 5 ml. acetic acid. Grease the upper half of the ground joint on the side arm and insert in flask. Weigh the sample of rosin acid (0.15-0.20 g.) to the nearest 0.0001 g. into a 9 x mm. sample cup. If the sample is a powdered solid, moisten with a drop of acetic acid. Place the sample cup in the neck of the flask where it is supported by the end of the stopper. Connect the flask to the gas buret using a thin film of grease on the ground glass joint, evacuate the apparatus and fill the same with hydrogen. Repeat the evacution and filling cycle four times. The final filling with hydrogen should almost completely fill the reservoir at the base of the buret. When this condition is reached, the flow of hydrogen into the buret is stopped by closing the proper stopcocks.

A magnetic stirrer is placed below the reaction flask and started. The speed is regulated so that stirring is just sufficiently vigorous to break the liquid surface. At this point reduction of the catalyst starts. When the catalyst is completely reduced to platinum black as evidenced by no further change in the mercury level (thisrequires "grams of sample This application is a continuation-impart.xof application-Serial No. 126,234.1'filed November -'8,

The. vinyl esters of f chemicallysstabilized trosin acids and polymers of said vinyl esters, disclosed herein, are claimed in application Serial No. 185,324, filed September 16, 1950, by John C. Robinson, Jr., and Walter S. Ropp.

What I claim and desire to protect by Letters Patent is:

1. A process for preparing a vinyl ester of a stabilized rosin acid which comprises vinylatin a stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a catalyst se lected from the group consisting of the carboxylic acid salts of zinc,mercury and cadmium and separating the resulting vinyl ester of the stabilized rosin acid from the other ingredients of the reaction mixture by distillation, the relatively crude ester product being directly distillable.

2. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a rosin acid by subjecting the said rosin acid to hydrogenation, then vinylating the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a catalyst selected from the group consisting of carboxylic acid salts of zinc, mercury and cadmium and separating the resulting vinyl ester of the stabilized rosin acid from the other ingredients of the reaction mixture by distillation.

3. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a rosin acid by subjecting the said rosin acid to hydrogenation, then vinylating the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a carboxylic acid salt of zinc as catalyst and separating the resulting vinyl ester of the stabilized rosin acid from the other ingredients of the reaction mixture by distillation.

4. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a resin acid by subjecting the said rosin acid to dehydrogenation, then vinylating'the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a catalyst selected from the group consisting of carboxylic acid salts of zinc,

11 mercury and cadmium and separating the resulting vinyl ester of the stabilized rosin acid from the other ingredients of the reaction mixture by distillation.

5. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a rosin acid by subjecting the said rosin acid to dehydrogenation, then vinylating the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a carboxylic acid salt of zinc as catalyst and separating the resulting vinyl ester of the stabilized rosin acid from the other ingredients of the reaction mixture by distillation.

6. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a 'rosin acid by subjecting the said rosin acid to hydrogenation until a hydroyenated rosin acid which is at least 40% saturated with hydrogen and which has a content of abietic-type resin acids of not over 10% is produced, then vinylating the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmospheric pressure in the presence of a catalyst selected from the group consisting of carboxylic acid salts of zinc, mercury and cadmium and separating the resulting vinyl ester of the 12 stabilized rosin acid from the other ingredients of the reaction mixture by distillation.

7. A process for preparing a vinyl ester of a stabilized rosin acid which comprises stabilizing a rosin acid by subjecting the said rosin acid to dehydrogenation until a dehydrogenated rosin acid having a dehydroabietic acid content of at least 40% and having an abietic-type resin acid content of not over 10% is produced, then vinylating the stabilized rosin acid by contacting the same in liquid phase with acetylene under superatmosphericpressure in the presence of a catalyst selected from the group consisting .of carboxylic acid salts of zinc, mercury and cadmium and separating the resulting vinyl ester of the stabi- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,066,075 Reppe Dec. 29, 1936 2,472,084 Beller et a1 June 7, 1949 

1. A PROCESS FOR PREPARING A VINYL ESTER OF A STABILIZED ROSIN ACID WHICH COMPRISES VINYLATING A STABILIZED ROSIN ACID BY CONTACTING THE SAME IN LIQUID PHASE WITH ACETYLENE UNDER SUPERATMOSPHERIC PRESSURE IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF CARBOXYLIC ACID SALTS OF ZINC, MERCURY AND CADMIUM AND SEPARATING THE RESULTING VINYL ESTER OF THE STABILIZED ROSIN ACID FROM THE OTHER INGREDIENTS OF THE REACTION MIXTURE BY DISTILLATION, THE RELATIVELY CRUDE ESTER PRODUCT BEING DIRECTLY DISTILABLE. 